1. Field of the Invention
The invention relates to a thin film magnetic head having at least a magnetoresistive element for reading out and a method of manufacturing the same.
2. Description of the Related Art
In recent years, performance improvement in thin film magnetic heads has been sought in accordance with an increase in surface recording density of a hard disk drive. As a thin film magnetic head, a composite thin film magnetic head has been widely used. A composite thin film magnetic head has a layered structure which includes a recording head with an inductive-type magnetic transducer for writing and a reproducing head with a magnetoresistive element (also referred as MR element in the followings) for reading-out. There are a few types of MR elements: one is an AMR element that utilizes the anisotropic magnetoresistance effect (referred as AMR effect in the followings) and the other is a GMR element that utilizes the giant magnetoresistance effect (referred as GMR effect in the followings). A reproducing head using an AMR element is called an AMR head or simply an MR head. A reproducing head using the GMR element is called a GMR head. The AMR head is used as a reproducing head whose surface recording density is more than 1 gigabit per square inch. The GMR head is used as a reproducing head whose surface recording density is more than 3 gigabit per square inch.
The AMR head includes an AMR film having the AMR effect. The GMR head has the similar configuration to the AMR head except that the AMR film is replaced with a GMR film having the GMR effect. However, compared to the AMR film, the GMR film exhibits a greater change in resistance under a specific external magnetic field. Accordingly, the reproducing output of the GMR head becomes about three to five times greater than that of the AMR head.
In general, an AMR element is a film made of a magnetic substance which exhibits the MR effect and has a structure of two to four layers. In contrast, most of the GMR films have a multi-layered structure consisting of a plurality of films. There are several types of mechanisms which produce the GMR effect. The layer structure of the GMR film depends on those mechanisms. GMR films include a superlattice GMR film, a granular film, a spin valve film and so on. The spin valve film is most sufficient since the film has a relatively simple structure, exhibits a great change in resistance in a low magnetic field, and is suitable for mass production. The performance of the reproducing head can be easily improved by, for example, replacing an AMR film with an MR film with high magnetoresistive sensitivity such as a GMR film.
Now, an example of a method of manufacturing a composite thin film magnetic head (AMR head) will be described with reference to FIG. 12 to FIGS. 19A, 19B as an example of a method of manufacturing a thin film magnetic head of the related art. FIG. 12 to FIG. 16 show an enlarged configuration of the air bearing surface (ABS) of the AMR head, respectively. FIG. 17A to FIG. 19A show the cross sectional configuration of the AMR head vertical to the air bearing surface while FIG.17B to FIG. 19B show the cross sectional configuration of the pole portion parallel to the air bearing surface, respectively.
First, as shown in FIG. 12, an insulating layer 102 made of, for example, alumina (Al2O3) is deposited to a thickness of about 5 to 10 xcexcm on a substrate 101 made of, for example, attic (Al2O3xe2x80x94TiC). Next, a bottom shield layer 103 for a reproducing head made of a magnetic material is formed in a thickness of about 2 to 3 xcexcm on the insulating layer 102. Next, a bottom shield gap film 105 as an insulating layer is formed through depositing, for example, alumina or aluminum nitride in thickness of 50 to 100 nm on the bottom shield layer 103 by sputtering. Next, a SAL (Soft Adjacent Layer) film 106a for applying bias magnetic field, a tantalum (Ta) film 106b as a magnetic isolation film and an AMR film 106c are formed on the bottom shield gap film 105 in this order.
Next, as shown in FIG. 13, a photoresist pattern 107 having a longitudinal bar 107a and a lateral bar 107b is selectively formed on the AMR film 106c. At this time, a photoresist pattern 107 with, for example, a T-shaped cross section is formed so that lift-off can be easily performed. Next, an AMR element 106 is formed through etching the AMR film 106c, the tantalum film 106b and the SAL film 106a to a taper shape by, for example, ion milling using the photoresist pattern 107 as a mask.
Next, as shown in FIG. 14, a pair of lead electrode layers 108 which are electrically connected to the AMR film 106c are formed on the shield gap film 105 by, for example, sputtering using the photoresist pattern 107 as a mask. The lead electrode layers 108 have a configuration in which a domain control film for suppressing noise made of, for example, cobalt-platinum alloy (CoPt) and a lead film for detecting signals made of, for example, titanium-tungsten (TiW) or tantalum are stacked, and are formed to cover the adjacent area of the end (side-end face and both end of the surface) of the AMR film 106c. 
Next, as shown in FIG. 15, the photoresist pattern 107 is lifted off. Then, although not shown in FIG. 15, another pair of lead electrode layers 111 (See. FIG. 17B) which are electrically connected to the lead electrode layers 108 are formed in a thickness of about 100 to 300 nm in a predetermined pattern. The lead electrode layers 111 are not exposed to the air bearing surface (ABS). Therefore, they are formed of a substance with low resistivity such as copper (Cu).
Next, as shown in FIG. 16, a top shield gap film 109 as an insulating layer is formed in a thickness of 50 to 150 nm on the lead electrode layers 108 and the AMR film 106c so as to bury the AMR element 106 in the shield gap films 105 and 109. Next, a top shield layer-cum-bottom pole (referred as a top shield layer in the followings) 110 made of a magnetic material, which is used for both a reproducing head and a recording head, is formed in a thickness of about 3 xcexcm on the top shield gap film 109.
Next, as shown in FIGS. 17A and 17B, a write gap layer 112 made of an insulating film such as an alumina film is formed in a thickness of 0.2 to 0.3 xcexcm on the top shield layer 110. Then, an opening (contact hole) 112a for a magnetic path is formed by partially etching the write gap layer 112 in a backward position (right-side in FIGS. 17A and 17B) of a region where thin film coils 114 and 115 are to be formed later. Next, a photoresist layer 113a for determining the throat height is formed in a thickness of about 1.0 to 2.0 xcexcm in a predetermined pattern on the write gap layer 112. Then, a thin film coil 114 for an inductive-type recording head is formed in a thickness of 3 xcexcm on the photoresist layer 113a. Next, a photoresist layer 113b is formed in a predetermined pattern on the photoresist layer 113a and the thin film coil 114. Next, a thin film coil 115 is formed in a thickness of 3 xcexcm on the photoresist layer 113b. Then, a photoresist layer 113c is formed in a predetermined pattern on the photoresist layer 113b and the thin film coil 115.
Next, as shown in FIGS. 18A and 18B, a top pole 116 made of magnetic materials for a recording head such as permalloy (NiFe) or nitride ferrous (FeN) is formed in a thickness of about 30 xcexcm on the write gap layer 112 and the photoresist layers 113a to 113c. The top pole 116 is in contact with and magnetically coupled to the top shield layer 110 through the contact hole 112a in the backward position of the thin film coils 114 and 115.
Next, as shown in FIGS. 19A and 19B, the write gap layer 112 and the top shield layer 110 are etched by ion milling using the top pole 116 as a mask. Next, an overcoat layer 117 made of, for example, alumina is formed in a thickness of 20 to 50 xcexcm on the top pole 116. Then, after completing the remaining steps for the wafer (description is omitted), the air bearing surface of the recording head and the reproducing head is formed by performing machine processing on the slider. Thereby, a thin film magnetic head is completed. As shown in FIGS. 19A and 19B, the configuration in which each sidewall of part of the top pole 116, the write gap layer 112 and the top shield layer 110 is vertically formed in a self-aligned manner is called a trim structure. With the trim structure, widening of the effective track width due to the spread of magnetic flux generated at the time of writing of the narrow track can be suppressed.
In a magnetic head manufactured as described, it is necessary to narrow the reading track width, for example, represented by W in FIG. 13, in order to improve the track density. In order to improve the output performance of a reproducing head, it is desired that the wiring resistance of the lead electrode layers 108 connected to the magnetoresistive element such as the AMR element 106 is low. However, the lead electrode layers 108 are exposed to the air bearing surface so that a material with low resistivity and less anticorrosive such as copper (Cu) can not be used. Therefore, in the related art, a method as follows is proposed: using tantalum (Ta), tungsten (W) or the like which has relatively low resistivity and is highly anticorrosive for the lead electrode layers 108; and thickening the film thickness of the lead electrode layer 108 so as to lower the wiring resistance.
In a manufacturing process of a magnetic head of the related art, the reading track width of a reproducing track is, for example, as shown in FIG. 13 to FIG. 15, determined by lift-off of the photoresist pattern 107. Therefore, it is necessary to increase the height A of the longitudinal bar 107a of the photoresist pattern 107 in order to thicken the lead electrode layers 108 connected to the AMR element 106. However, if the height A of the photoresist pattern 107 is increased, narrowing the width (length of the lateral bar 107b) and the reading track width W becomes difficult. As described, in the process of the related art, it is difficult to narrow the reading track width W of the AMR element 106 while thickening the film thickness of the lead electrode layers 108 to lower the wiring resistance of the electrode.
Also, if the thickness of the lead electrode layer 108 is simply thickened, the wiring resistance decreases. However, changes in the shape of the top shield layer become large by doing so and its characteristic is deteriorated.
For example, Japanese Patent Application laid-open Hei 6-180825 discloses a technique of decreasing the wiring resistance by increasing the cross sectional area through adding another conductive layer so as to cover a part of the conductive layer (lead electrode layer) connected to a magnetoresistive element. Also, Japanese Paten Application laid-open Hei 7-302414 discloses a technique in which the configuration of a lead structure (lead electrode layer) is made to include high-conductive metal and heat proof metal. Japanese Patent Application laid-open Hei 3-30107 discloses a technique in which the film thickness of a lead electrode layer becomes thicker as it becomes distant from the reading track of a magnetoresistive element. However, none of those techniques mentions a method of solving problems raised when thickening the film of the electrode layer. Therefore, there still exists a problem that it becomes harder to narrow the reading track width as the lead electrode layer is formed thicker.
The invention has been designed to overcome the foregoing problems. The object is to provide a thin film magnetic head in which the wiring resistance of a lead electrode layer connected to a magnetoresistive element is decreased even if the reading track width becomes narrow so that the track density is improved, and a method of manufacturing the same.
A thin film magnetic head of the invention comprises: a magnetoresistive element; two shield layers placed to face each other sandwiching the magnetoresistive element in between to shield the magnetoresistive element; an insulating layer provided between the magnetoresistive element and each of the shield layers; and a lead electrode layer, which is electrically connected to the magnetoresistive element, provided on one side of a substrate; wherein: a convex portion corresponding to the reading track width of the magnetoresistive element is provided on one of the shield layers.
A method of manufacturing a thin film magnetic head of the invention: comprising a magnetoresistive element; two shield layers placed to face each other sandwiching the magnetoresistive element in between to shield the magnetoresistive element; an insulating layer provided between the magnetoresistive element and each of the shield layers; and a lead electrode layer, which is electrically connected to the magnetoresistive element, provided on one side of a substrate; includes the steps of: forming a bottom shield layer which is one of the two shield layers; forming a concave portion corresponding to the reading track width of the magnetoresistive element in the surface of the bottom shield layer; forming the insulating layer on the bottom shield layer where the concave portion is formed and forming the magnetoresistive element thereon; and forming the lead electrode layer so as to electrically connect to the magnetoresistive element on the insulating layer.
In a thin film magnetic head and a method of manufacturing the same, the convex portion corresponding to the reading track width of the magnetoresistive element is provided on one of the shield layer. As a result, the film thickness of a lead electrode layer which is electrically connected to a magnetoresistive element along one of the insulating layer can be thickened while decreasing the width of the photoresist pattern used at the time of forming the lead electrode layer. Thereby, the reading track width can be narrowed.
In a thin film magnetic head of the invention and a method of manufacturing the same, an insulating layer other than the insulating layer provided between the bottom shield layer and the magnetoresistive element may be formed on the surface of the bottom shield layer on the side where the convex portion is formed; and a step may be provided between the surface of the convex portion of the shield layer and the surface of the other insulating layer. Thereby, the insulating characteristic between the lead electrode layer and the bottom shield layer can be improved without thickening the insulating layer between the magnetoresistive element and the bottom shield layer.
In a thin film magnetic head of the invention and a method of manufacturing the same, the sidewall surface of the convex portion of the bottom shield layer may form a slope toward the surface of the bottom shield layer on the side where the convex portion is formed.
In a method of manufacturing a thin film magnetic head of the invention, the other insulating layer having a step between the surface of the convex portion may be formed by performing flattening process through polishing an insulating material until the surface of the convex portion is exposed after depositing the insulating material all over the surface of the bottom shield layer where the convex portion is formed.
In addition, in a method of manufacturing a thin film magnetic head of the invention, the convex portion may be formed using a mask in the step of forming the convex portion of the bottom shield layer; and then after depositing an insulating material on the bottom shield layer and the mask, the insulating material on the convex portion is removed by removing the mask in the step of forming the other insulating layer.
In a method of manufacturing a thin film magnetic head of the invention, the convex portion of the bottom shield layer can be formed by milling method using a photoresist pattern as a mask. In this case, it is desired that the photoresist pattern has a T-shaped cross section.
In a thin film magnetic head of the invention and a method manufacturing the same, the width of the convex portion of one of the shield layer (or the bottom shield layer) may be narrower or wider than the reading track width. However, it is preferable that the difference lies within the range of +1 and xe2x88x921 xcexcm of the reading track width.
Other and further objects, features and advantages of the invention will appear more fully from the following description.